Conventionally, parallel data transfer has been employed for multi-bit data transfer. In parallel data transfer, multi-bit data is concurrently transferred using plural signal lines, each of which is assigned to each of the multiple bits. However, when the number of bits in the concurrent transfer increases to, e.g., 8 bits, 16 bits, 32 bits, and 64 bits, it causes a problem of an increased number of data signal lines in the parallel transfer. In view of this, serial data transfer, in which data transferred while being shifted in synchronization with a clock signal is enabled by a strobe signal, has come into use.
Taking, for example, a printing apparatus which performs printing by reciprocally scanning an inkjet printhead (hereinafter referred to as the printhead) mounted to a carriage, various control signals and data signals are transmitted or received between the printhead and the printer main unit through a flexible printer cable (FPC) that connects the carriage and the printer main unit. For the data transfer between the printhead and the printer main unit, the serial transfer method is adopted.
Furthermore, such a printing apparatus comprises a carriage motor for driving a carriage, a conveyance motor for conveying a printing medium such as printing paper, and various other motors. These motors are driven by motor drivers. For transferring motor driving signals from the control circuits of the printing apparatus to the motor drivers, the serial transfer method is also adopted. Since the types and driving methods of the various motors are different in accordance with their usage, different types and different numbers of control signals are transferred to respective motor drivers, and the motor drivers are required to execute motor driving control. For this reason, conventionally, dedicated motor drivers corresponding to respective motors are provided to individually perform motor driving control.
Furthermore, in a case of transferring data in accordance with plural different factors, there has been a method proposed to realize data transfer where a data signal, a clock signal, and a strobe signal are assigned for each factor, and a control signal is added for switching over between the factors.
For instance, Japanese Patent Application Laid-Open (KOKAI) No. 8-130621 and No. 9-207369 disclose such technique.
Moreover, Japanese Patent Application Laid-Open (KOKAI) No. 2001-223596 proposes execution of data transfer at the rising edge of a strobe signal.
However, assume that the above-described conventional serial transfer method is applied to the data transfer between the control circuits and the motor drivers of the aforementioned printing apparatus. Under ordinary circumstances, the serial data transfer can be realized by three signal lines respectively supplying three signals: a clock signal, a data signal, and a strobe signal. However, for instance, when more than three signal lines become necessary due to the increased types and numbers of motors, the number of signal lines naturally increases. Along with the increase, it becomes necessary to largely change the specification of the printing apparatus, e.g., providing new signal pads for the control circuits and motor drivers, enlarging the layout area of the circuit board for arranging the increased number of serial signal lines on the control circuits, and so forth.
In addition, if dedicated motor drivers corresponding to various motors provided in the printing apparatus are used for individual motor driving control as has been adopted conventionally, different types of motor drivers become necessary, and the cost for developing such motor drivers becomes extremely high. On the other hand, there are demands for reducing the development cost arising from the different driving methods and types of motors as well as the increased number of signals.
Furthermore, assuming that the above-described conventional serial transfer method is applied to the data transfer between the printhead and the head driver of the aforementioned printing apparatus, if the number of signals larger than the conventionally used number becomes necessary due to increased functions of the printhead, the number of signal lines naturally increases. Along with the increase, a change in the specification becomes necessary, e.g., providing new signal pads in the printhead, increasing pins and pads for electric connections in the carriage, enlarging the width of the flexible printer cable (FPC), increasing the number of connection pins in the printhead interface of the head driver IC which is provided in the printer main unit for driving the printhead, and so forth.
Therefore, if the number of signal lines increases due to the increased functions of the printhead, it becomes necessary to change the specification and add functions of the head driver that drives the printhead. This leads to upsizing of a driver IC that realizes the head driver, resulting in an increased production cost of the overall printing apparatus.
As described above, in a case of applying serial data transfer to an inkjet printing apparatus, an increase in the number of signal lines gives impact in various aspects.
Meanwhile, the demands for adding functions in the printing apparatus and/or the printhead is a trend of the times. Also, developing and providing high-performance printers and printheads that meet various market demands are requirements that should be considered.
In view of the above, although the increased number of signals is inevitable to realize advanced functions of a printing apparatus or a printhead, it is required to realize serial data transfer while suppressing an increase in the number of signal lines.